1. Field of the Invention
The present invention relates generally to optical waveguide based switches and more particularly to a three-dimensional, rewriteable, waveguide switch in a photosensitive medium.
2. Discussion of the Related Art
Fiber optic networks for transmission of optical signals have come into wide use for telecommunications and data communications in recent years. These fiber optic networks need rapid, efficient and effective switching apparatus to switch one or more incoming channels to one or more other channels within the network. Several switching techniques and structures have been developed in recent years that are satisfactory for many applications for switching one or more incoming channels from one or more paths to one or more other paths. However, in general these are not entirely satisfactory for many applications, including large cross-connect switches.
Several cross-connect switches using a waveguide matrix have recently been developed. However these optical waveguide based matrix switches are based on two-dimensional, planar lightwave circuits (bubble switches) or free space switches using microelectromechanical systems (MEMS) (tilting mirrors). The waveguide approach overcomes some of the problems of the MEMS approach in that the device is minimally sensitive to mechanical vibrations and thermal fluctuations. However, the MEMS approach takes advantage of 2N(1XN) switching architecture and free space beam propagation in order to minimize losses that increase with port count. A number of switch structures of this type are disclosed in U.S. Pat. Nos. 5,699,462 and 5,960,131. In general, an optical signal must traverse between one and (2* N)xe2x88x921 points in an N*N matrix switch.
Accordingly, there is a need for an improved waveguide based switch that has the advantages of both of the aforementioned approaches. The present invention satisfies this need and provides other related advantages as well.
It is one purpose of the present invention to provide a waveguide based matrix switch that overcomes the above problems of the prior art by providing a rewriteable, three-dimensional switch.
In one aspect of the invention, an optical switch has a photosensitive substrate with a plurality of surfaces, a plurality of inlet ports in one of the plurality of surfaces, and a plurality of outlet ports in another of the plurality of surfaces. It also has a source of at least two light beams, and a means for directing the light beams at a selected line of intersection drawn between one inlet port and one outlet port, thereby creating a waveguide.
In additional embodiments, the invention has a photosensitive substrate with at least one surface, at least one inlet port in one surface and at least one outlet port in the same surface of the substrate. It also has a source of one light beam, a means for splitting the light beam into at least two light beams, and a means for focusing the two light beams at a selected location line drawn between one inlet port and one outlet port, thereby creating at least one waveguide in the photosensitive substrate.
The invention also provides a method of forming a waveguide in a substrate by taking a three-dimensional photosensitive substrate having a plurality of planar surfaces, the photosensitive substrate comprising a plurality of inlet ports in one of the plurality of surfaces, and a plurality of outlet ports in another one of the plurality of surfaces. The method also includes adding a source of at least two light beams and focusing the light beams at a selected line of intersection drawn between one inlet port and one outlet port to change the refractive index of the photosensitive substrate at the line of intersection, thereby creating a waveguide in the substrate.